This page describes which parts you need to build revision 5 of the LAOS mainboard. The revision 5 mainboard is a completely redesigned version of the mainboard. It is still compatible with the older versions but the layout has changed.

Before ordering the parts a few choices have to be made:- External stepper drivers or Pololu 1182 stepper drivers. If you are going to use external stepper drivers, you can omit the Pololu drivers and their capacitors (100uF: C9, C10, C11)- Power source for the mBed: if there is a stable 5V power source available in you laser cutter you can omit the 7805 and bridge VCPU to +5V on U3.- Connectors: HPC's lasers use JST connectors, the footprints of the connectors also allow for 5.08mm pitch connectors like a Phoenix contact MSTBA on the PCB and MSTB on the cable.- Switching output: Q1 and Q2 can host heavy NPN transistors/mosfets that can be used to switch external loads. If you don't want to do that you can omit J27, Q1, Q2, R17 and R15.- SD card or microSD card: since revision 5 there is an option to mount a microSD card holder instead of the full size SD card holder. Where the regular SD card sticks out of the board, the microSD card stays inside the board. The microSD card holder is harder to mount and some microSD cards may not work with the board (SPI support is not mandatory for microSD cards). When in doubt: use the regular one. There are connection issues with the microSD, before mounting a microSD card holder, please read about know issues on the forum!: http://redmine.laoslaser.org/boards/1/topics/689?r=729#message-729

Some parts are not (yet) supported in the software and are therefore not neccesary:- USB connector (J1)- CAN bus (CAN1, R1, U1, C2)

Both 2.54mm pitch connectors and 5.08mm pitch connectors fit in the board. The reference design uses Phoenix MSTBA and MSTB connectors, which are compatible with the sometimes cheaper Wurth elektronik series 351 and 313. The HPC LS3020 (pro) uses low cost JST connectors and a flatcable. The choice is yours, if you want to keep the original connectors you can use the JST connectors, if you want stronger and more solid connectors you can use the larger ones.

Note that the connectors to the stepper motor(driver)s (J9, J18 and J24) have 5 pins. You need usually only 4 of them; when using Pololu's you need the + and - for coil A and coil B. For external stepper drivers you need E, S and D and either + or GND. If you really need both + and GND get PCB headers with open sides instead of closed sides like the ones above because 5 pin PCB headers with closed sides will not fit.

If your laser does not have a good 5V power supply built-in, you can add this 7805 power regulator. Note that it will get very hot if you feed it a high voltage. Anything between 7 and 12 volt should be ok. You can use a left-over power adapter to power the board.

Collect all the parts, put on your favorite music and heat up your soldering iron.First solder the SD-card connector; it's recommended to use a fine tip for the small legs of the connector. (The pictures are a tiny bit different from the actual rev 0.5 board because this was a pre-production version).

It's usually the easiest to solder the low parts first; in this way when you put the part in the board and flip it over the part will stay in the board because it lies directly on the table. If other parts were higher the part would fall out.The lowest part here are the resistors, followed by the leds, ceramic capacitors, jumpers, connectors, electrolytic capacitors and finally the 7805 and large transistors.

If you use external stepper drivers you need to make 4 bridges. Refer to the "External stepper driver" drawing on the PCB.

Refer to the following image for the correct orientiation of the flatcable connector:

J28: Vout for the high current outputs. This configures what is connected to Vout on J27. This can either be +5V; the stabilized 5V output, or VCPU; the unstabilized VCPU input where the +5V is derived from.

J40: VMOT/VCPU bridge: bridge this jumper if you want to use the same powersource for VMOT and VCPU

J7, J16, J22: microstepping: with these solderbridges the microstepping setting can be configured: the default is 16: all bridges connected. If you want something else you need to carefully remove the existing connection between the pads with a sharp knife or a Dremel. Refer to the table on the underside of the PCB for the settings.

J12, J19, J25: GND connection for the stepper motor connectors; these bridges are connected by default. If you don't want GND on pin 5 of J9, J18 or J24 remove the connection between the pads.

J3: CPU power from USB. You don't want this.

J41: O1 Source: dependent on what you want: laser enable of laser on

J42: O2 source: dependent on what you want: exhaust enable or laser PWM

If you are absolutely sure all power connections are OK, install the other components and proceed with the functional tests.

WRONG JUMPER CONNECTIONS OR BAD SOLDERING CAN CAUSE YOUR COMPONENTS (OR EVEN YOUR COMPUTER) TO START SMOKING AND CAUSE A LOT OF DAMAGE, MAKE SURE YOU CHECK AND DOUBLE-CHECK EVERYTHING BEFORE CONNECTING THINGS